1. Field of the Invention
This invention relates generally to differential pressure transducers and more particularly to differential pressure transducers employing aneroid capsule diaphragms as pressure sensing elements.
2. Description of the Prior Art
Differential pressure transducers are known in which a rigidly connected pair of aneroid capsule diaphragms are constrained to flex cooperatively upon the application of differential pressures to its inlet ports. The resultant displacement is toward the lower pressure and the magnitude of the displacement is proportional to the differential between the applied pressures.
In one application, for example, the pressure incident upon a reference compartment of a differential pressure capsule may be reduced below that unknown pressure to be incident upon the other compartment. Applying this unknown pressure to this other compartment, the reference pressure may be built up in a series of small pressure increments. When the two pressures are made equal, within the limits of the sensitivity of the differential pressure capsule and within the resolution of the small pressure increments, that event can be observed by the closing of a contact located on a diaphragm situate between the two pressures.
Other approaches may be examined by reference to the prior art. A patent application, Ser. No. 673,493, filed 4/5/76 and assigned to the same assignee as the present patent application, describes motion sensing means similar to that utilized in the present invention. One such system is described in U.S. Pat. No. 3,901,082 to Lyon for Fluid Pressure Sensing System and Differential Pressure Unit Therefore. Another such system is defined in U.S. Pat. No. 3,882,443 to Martia for Differential Pressure Transducer.
Many prior art devices have been developed as particular solutions to specific problems and thus have served narrow purposes. Applicant does not know of a prior art system that provides isolation for the mechanism of the pressure transducer by means of fluid linkage along with the other advantages of the present invention. While presently available differential pressure transducers can measure differential fluid pressures, some of the disadvantages of these prior art transducers include the incidence of the media upon the sensing elements of the transducer. Such physical contact may be undesirable for a variety of reasons, among which may commonly be listed corrosive media, for example.
It would thus be a great advantage to the art to provide a differential pressure transducer in which the fluid media under the pressure to be determined need not come into direct contact with the sensing elements thereof.
Another great advantage would be the provision of a differential pressure transducer that has inherent protection against high line pressure overloads.
A further desirable advantage would be to provide such a transducer with an easy electrical readout capability.